Bending an optical fiber into backplane

ABSTRACT

A right angle bend mount for bending an optical fiber into the plane of a circuit board. The mount includes a base and a cover that is pivotably connected to the base by a hinge. A clamp is formed by a first pair of opposed surfaces of the base and cover adjacent the hinge. This clamp fixedly grips a ferrule portion of the optical fiber when the base and the cover are closed together. A second pair of opposed surfaces of the base and coverforms another clamp. This clamp fixedly grips a non-ferrule portion of the optical fiber when the base and the cover are closed together. A bent portion of the optical fiber between the ferrule portion and the gripped non-ferrule portion is disposed in a non-gripping gap between the base and the cover when the base and the cover are closed together.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 10/618,786, filed onJul. 14, 2003, now U.S. Pat. No. 6,782,181, issued on Aug. 24, 2004,which is a continuation of U.S. Ser. No. 10/179,756, filed Jun. 25,2002, now U.S. Pat. No. 6,594,435, which claims priority to theprovisional patent application identified by the U.S. Ser. No.60/300,878, filed Jun. 26, 2001, of which the entire content of eachapplication is hereby expressly incorporated by reference.

INTRODUCTION

The present invention relates generally to the field of opto-electronicprinted circuit boards. More particularly, the present invention relatesto integration of a fiber management system into a backplane printedcircuit board via a right angle bend mount.

BACKGROUND OF THE INVENTION

Optical fiber as used in standard telecommunications and otherapplications is based upon the principles of Snell's Law and totalinternal reflection. Each fiber is made up of a central core and anouter layer known as the cladding. By establishing a core with an indexof refraction (n) higher that the index of refraction of the cladding,the light will totally reflect internally rather than passing throughthe core and being lost.

Optical fiber connectors are made possible through the employment of adevice known as a ferrule. This device supports and aligns the fiberallowing for a precise coupling of one fiber to another when theconnection is made. In the case of a single fiber connector, the ferruleis a cylindrically shaped structure, often ceramic, which holds thefiber in its center with the aid of a cured epoxy resin. The end of thefiber and the ferrule are polished to create an optically smooth, largeplanar surface with the optical fiber aligned as close as possible tothe center of the device. When two keyed ferrules are aligned end to endthrough a mechanical connector, optical coupling takes place between thetwo fibers allowing the optical connection to be made. Often, thejoining ferrule surfaces are not orthogonal in order to reduce unwantedreflection.

Multiple fiber connectors employ a ferrule that is generally rectangularin shape with grooves or holes allowing for precise alignment of aplurality of fibers. These fibers are supported in a single, parallelarray, separated by 250 microns on center.

It is desirable to interface optical fibers and optical fiber arrayswith a printed circuit board so that they lay along the surface of theboard and then bend into the board so that they form a right angle withthe surface of the board. Optical fiber as used in standardtelecommunications and other applications is limited by its physicalstructure in its ability to make a right angle transition. Physicallybending the fiber at such a right angle may cause strain that leads tofractures and structural imbalances in the fiber material. Repeatedflexing of fibers bent in such a way exacerbates the failure risk.

Thus, what is needed is a way to make an abrupt right angle bend of anoptical fiber or fiber array into a printed circuit board in a mannerthat is stable and prevents repeated flexing.

SUMMARY OF THE INVENTION

It is an object of the present invention to bend an optical fiber tocreate a back panel/circuit-pack interface.

It is another object of the present invention to effect bending of anoptical fiber into a backplane panel by mounting the fiber-array andguiding it with a molding shaped and dimensioned so that the stress onthe fiber is minimized and radius of the bend fiber is maximized.

It is yet another object of the present invention to provide a rightangle bend mount that easily mounts to a printed circuit board.

It is still another object of the present invention to provide a rightangle bend mount having an easy locking V-groove structure.

It is a further object of the present invention to provide a right anglebend mount that mounts in a backpanel with automatic orientation.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention will beapparent in the following detailed description read in conjuction withthe accompanying drawing figures.

FIG. 1 illustrates a perspective exploded view of a right angle mountaccording to an embodiment of the present invention.

FIG. 2 illustrates a perspective view of the right angle mount of FIG.1, assembled with a fiber array and embedded in a backplane.

FIG. 3 illustrates a sectional elevation view of the right angle mountof FIG. 1, assembled with a fiber array and embedded in a backplane.

FIG. 4 illustrates a plan view of the right angle mount of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention pertains to electro-optical backplane systems thatemploy optical fibers. The present invention is applicable for any fiber(single mode, multimode, polymer fiber) provided that the fiber canphysically make a small bend radius with acceptable loss. The type ofapplication (i.e., frequency range used) determines, in part, the lossin the system. The most useful fibers for this system are those thatallow for a small bend radius. An exemplary embodiment of the presentinvention is a right angle bend mount for bending an optical fiber intothe plane of a circuit board. This right angle bend mount includes abase and a cover that is pivotably connected to the base by a hinge. Aclamp is formed by a first pair of opposed surfaces of the base andcover adjacent the hinge. This clamp fixedly grips a ferrule portion ofthe optical fiber when the base and the cover are closed together. Asecond pair of opposed surfaces of the base and cover forms anotherclamp. This clamp fixedly grips a ferrule portion of the optical fiberwhen the base and the cover are closed together. The ferrule portion ofthe optical fiber is held at a right angle to the gripped non-ferruleportion of the optical fiber when the base and the cover are fixedtogether in a closed position. A bent portion of the optical fiberbetween the ferrule portion and the gripped non-ferrule portion isdisposed in a non-gripping gap between the base and the cover when thebase and the cover are closed together.

According to an exemplary embodiment a fiber management system (or“FMS”) is terminated with a ferrule (single or array). The illustratedexemplary embodiment uses an array type “MT” connector. The fiber typeused in the FMS also determines, in part, the loss in the system as itwill be bent in a radius of about 8-10 mm. Fibers with high differencesin a refraction index or doping are useful to keep the losses low.

Referring to FIG. 1, the MT connector (shown in phantom) is illustratedmounted in a right angle mount (or molding) 100. The mount 100 guidesand holds the fibers of the FMS in position to prevent signaldistortion. The mount 100 is shaped in way such that it can be lockedand fixed into the backplane 200. Referring to FIG. 2, a perspectiveview of the right angle mount 100 of FIG. 1 is illustrated, assembledwith a fiber array and embedded in a backplane 200. In this view, themount 100 is shown locked and fixed into the backplane 200. The MT fiberarray is shown in phantom.

Referring to FIG. 3, a sectional elevation view of the right angle mount100 of FIG. 2 is illustrated, assembled with a fiber array and embeddedin a backplane 200. A silicon V-groove structure 110 helps to hold theMT fiber array 50 in place. A gap 120 is formed inside the mount 100 toprovide extra space that permits some variance in how the fiber array 50bends inside the mount 100. Snap connectors 130 hold the mount 100 in aclosed position.

Referring to FIG. 4, a plan view of the right angle mount 100 of FIG. 2is illustrated.

The manufacturing method of how to aligned and mount the fiberconnector/fiber array connector into the backplane is considered noveland, due to its simplicity, cost-effective. The exemplary embodimentuses component that are either readily available or easy to manufacture.The main element is a molded mount for PCB mounting.

This concept illustrated by the exemplary embodiment separatestraditional backplane manufacturing from backplanes that are trulyintegratable with an optical fiber management system.

One advantage of PCB manufacturing using the exemplary embodiment isthat expensive components for the optical circuitry are notlost/scrapped in the case of a defect electrical circuit due to amanufacturing failure. The system is modular and parts may be exchangedor saved in the manufacturing process, thus saving money. The presentinvention has been described in terms of an exemplary embodiment,however, it will be appreciated that various modifications andimprovements may be made to the described embodiment without departingfrom the scope o f the invention.

1. An electro-optical assembly, comprising: an optical fiber; a backplane defining an opening; and a bend mount positioned within theopening formed in the back plane, the bend mount comprising: a basedefining a curved surface; a cover connected to the base such that aportion of the cover is positioned adjacent to the curved surface of thebase, the optical fiber being positioned on the curved surface of thebase such that the base and the cover cooperate to bend the opticalfiber.
 2. The electro-optical assembly of claim 1, wherein the bendmount further comprises a first clamp formed by a first pair of opposedsurfaces of the base and cover, the first clamp adapted to fixedly gripa ferrule portion of the optical fiber when the base and the cover arefixed together in a closed position.
 3. The electro-optical assembly ofclaim 2, wherein the bend mount further comprises a second clamp formedby a second pair of opposed surfaces of the base and cover, the secondclamp adapted to fixedly grip a non-ferrule portion of the optical fiberwhen the base and the cover are fixed together in a closed position; 4.The electro-optical assembly of claim 1, wherein the bend mount furthercomprises a second clamp formed by a second pair of opposed surfaces ofthe base and cover, the second clamp adapted to fixedly grip anon-ferrule portion of the optical fiber when the base and the cover arefixed together in a closed position;
 5. The electro-optical assembly ofclaim 1, wherein a bent portion of the optical fiber is disposed in anon-gripping gap between the base and the cover when the base and thecover are fixed together in a closed position.